High integration and refinement of a semiconductor element has been improved from a design rule 45 nm node to 32 nm node; further, the development of a semiconductor element with the node of 22 nm or less has been in progress. In order to achieve these high integration and refinement of a semiconductor element, presently used technique is a photolithography technique for transferring a pattern on a wafer by using a photo mask by means of an optical projection exposing apparatus utilizing an ArF excimer laser with the light exposure wavelength of 193 nm. In the photolithography technique, rapid development and practical application of techniques for high resolution by using a light exposing apparatus, such as a high NA light exposing technique in which the numerical aperture (NA) of a projection lens is increased, a liquid immersion light exposing technique in which the light is exposed to a target via a high-refractive medium disposed between the projection lens and the target, and a modified-light installed light exposing technique have been rapidly are under way.
Under such circumstances, a super resolution technique (RET technique: Resolution Enhancement Technique) has been suggested in recent years, in order to improve the resolution level. Examples of such super resolution technique may include a method such that a mask pattern is optimized by applying an auxiliary pattern and bias (correcting amount of a mask line width, for example) to the mask pattern in accordance with the light exposing optical property, and a method called a modified lighting method (also called as an oblique light incidence lighting method). Lightings such as a zonal ray lighting using a pupil filter, a dipole lighting using a dipole pupil filter, and a quadrupole (C-quad) lighting using a quadrupole pupil filer are usually used for the modified lighting method.
On the other hand, as a measure for improving the resolution level in a photo mask (also called as a reticle) used for a photolithography technique, refinement and improvement in accuracy of a conventional binary type photo mask (hereinafter referred as binary mask) in which a pattern is designed in the portion of transmitting light and portion of shielding light by forming a light-shielding film using chrome for example on a transparent substrate; and development and practical application of phase shift masks such as a Levenson type phase shift mask for enhancing the resolution level improvement by means of the phase shift effect utilizing interference of light, a half tone type phase shift mask comprised of a light transmitting portion and half-transmitting portion, and a chrome-less type phase shift mask in which a light-shielding layer such as chrome is not arranged, have been in progress.
The above-described half tone type phase shift mask has a mask pattern comprised of a half-transparent film (hereinafter also referred to as a half-transparent pattern film) on a transparent substrate as a typical constitution, and is designed in the manner that the phase of exposure light transmitted to this half-transparent pattern film and the phase of exposure light transmitted to the transparent substrate are reversed.
In such half tone type phase shift mask, decrease in optical strength due to the phase reversing occurs at the border between the half-transparent pattern film arranged portion (hereinafter also referred to as a mask pattern portion) and a transparent substrate exposed portion, so as to prevent the optical strength distribution from being spread. In terms of a material for the half-transparent film, a compound of molybdenum silicide (MoSi), such as molybdenum silicide oxide nitride (MoSiON), is widely used.
Here, a transmittance of the half-transparent pattern film is conventionally designed to be approximately 6%, but the problem is that a transferred image becomes unclear due to the exposure light transmitted to this half-transparent pattern film, in the place where an area of the mask pattern portion is large. Under such circumstances, a constitution of shielding unnecessary exposure light certainly by arranging a light-shielding portion (hereinafter also referred to as a light-shielding pattern film) on a half-transparent pattern film has been suggested. (Refer to Cited Document 1 for an example.) A half tone type phase shift mask with such constitution is called as a try tone mask.
Here, a light-shielding pattern film of a try tone mask with high transmittance rate in a half-transparent film suitably used for forming a minute dot pattern and hole pattern requires thickness since higher light-shielding property is necessary for the light-shielding pattern film on the half-transparent pattern film.
However, if the light-shielding pattern film is thickened, a resist pattern for processing the light-shielding pattern film is also required to be thickened, which makes the processing of a fine pattern difficult. Also, a malfunction such as a pattern collapse during washing may be caused since the heights of the light-shielding pattern film and half-transparent pattern film are increased in the step of processing a mask.
Also, with regard to a binary mask to be used for a half-pitch (hp) of a pattern on a wafer from 40 nm on, the width of a mask pattern line on a photomask becomes smaller than the wavelength 193 nm of ArF excimer laser exposure light to be used for a lithography; a problem is that a value of bias (EMF bias) which is a correcting amount of a mask line width derived from the effect of an electro magnetics field (EMF) increases when the film thickness of a light-shielding pattern film in a mask pattern region is thick, since an oblique light incidence lighting method and a super resolution technique using a pupil filter have been adopted in order to form a fine pattern.
Then, such a problem arises also in a half tone type phase shift mask (try tone mask) having the above described light shielding pattern film.
Under such circumstances, with regard to the above described problem caused by the effect of an electro magnetics filed (EMF), a material for a mask has been reconsidered also in a half tone type phase shift mask (try tone mask) having the above described light shielding pattern film, and a try tone mask using a molybdenum silicide (MoSi) based material as a light-shielding pattern film material other than a chrome based material has been suggested in recent years (for example, refer to Patent Document 2).